For ease of reference only the present invention will now be discussed in relation to farm tractors. However, this should not be seen as limiting the scope of the resent invention which has applications to other vehicles and other towing operations.
At present problems are often typically encountered when vehicles such as farm tractors are used for towing device such as above ground working implements including seed drills, scoops, large trailers and cultivating discs. In general, these problems arise due to the tractor and/or towed implement encountering:                Obstructions e.g. rocks        Muddy or wet ground        Hills or hollows        
The above situations cause problems as they can adversely affect the traction of the tractor's driving wheels and render the towing of such implements a dead weight dragging operation.
The above difficulties are currently overcome by using tractors which have:                Ballast added; or        Increased horse power/weight; and/or        Four wheel drive; and/or        Dual wheels        
However, as will be appreciated the above remedies suffer from either increasing the cost of the tractor required to perform the job, or add time and effort to the job in relation to adding ballast to the tractor.
In relation to underground working implements such as ploughs and rotary hoes the above mentioned difficulties for towed implements have been overcome by the implementation of a hydraulic draft control system associated with the three point linkage of a tractor. The draft control system operates by either raising or lowering the implement depending on whether its effective load has been increased or decreased. By this, means the draft control system is able to transfer load (weight) between the implement and tractor to maintain the desired degree of wheel slippage.
The inventor's previous apparatus for addressing these problems is described in U.S. Pat. No. 6,533,307. Whilst this apparatus is very effective at overcoming these difficulties it requires the tractor to have a draft control system which is not always present on many tractors particularly in North America. The present invention therefore allows for the effective transfer of the towed load to the tractor, to avoid or at least significantly reduce, wheel slippage, without the need to utilise a draft control system.
The present invention is also particularly concerned with dispensing with the need for tractors to carry additional ballast sometimes in the order of 1.5-10 tons in order to prevent wheel slippage.
It would therefore be an advantage if there could be provided some means by which the draft control system already present on many tractors could be utilised in the towing of above ground implements also.
It would also be useful if there could be provided a load transfer apparatus and/or method of load transfer which could improve the towing and/or braking ability of road vehicles towing a load.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word “comprise”, or variations thereof such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.